Apparatus for cleaning ducts



Jan. 22, 1963 J. H. DOWNING 3,074,098

APPARATUS FOR CLEANING DUCTS Filed March 21, 1960 2 Sheets-Sheet 2 12 217.3 ll] x 48 I. 33

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INVENTOR. Join A! bowl/1 ire This invention provides an apparatus for the cleaning of ducts, such as air ducts of heating, air conditioning, ventilating, and exhaust systems. It is also suitable for use in the fireproofing of grease-collecting ducts, by applymg a suitable adherent fireproof coating thereto, such as lime, instead of a blast-cleaning fluid.

The present invention provides an apparatus which provides a rotating high pressure blast of fluid which is aimed at the wall of the duct, at an angle thereto. Normally the fluid medium of the blast carries a suspension of abrasive particles such as sand, but in some cases it may constitute a fluid such as steam. The high pressure blast, striking the wall of the duct at an angle, produces a tearing or scouring effect along the wall, removing dirt from the wall. At the same time, it moves the dirt forwardly to the end of the duct, where it can be collected. The rotation of the blast makes certain that all parts of the wall will be cleaned as the portable unit is advanced in the duct.

The apparatus of the present invention utilizes the high pressure of the fluid for rotating a set of blasting nozzles. This rotation is produced by a separate set of tangential nozzles.

I have found that if the blast nozzles have a substantial tangential component, this greatly reduces the blast pressure against the wall of the duct, thereby tending to defeat the purpose of the apparatus. Thus, by completely eliminating any such tangential component of the blast nozzles, maximum cleaning effect is obtained. Thus, I utilize non-tangential nozzles for blasting the wall of the duct, and separate tangential nozzles for rotation of the system including the blast nozzles. In some cases, however, 1 may adjust the blast nozzles to possess a slight tangential component, but this will be so oriented as to produce a counter-rotational thrust instead of a propulsive thrust. This permits fine adjustment of rotational speed without reducing the blast pressure; in fact it somewhat increases the blast pressure.

Thus, an object of the present invention is to provide an apparatus of the aforesaid type which utilizes the pressure of the fluid for rotating the blast nozzles, without substantially decreasing the blast pressure against the wall of the duct.

Another object of the invention is to provide separate blast and propulsion nozzles for such an apparatus.

Another object of the invention is to provide such an apparatus, having a readily adjustable speed of rotation.

Another object of the invention is to provide such an apparatus which is readily utilizable in square or round ducts. Other objects and advantages of the invention will more fully appear from the following description, taken in connection with the accompanying drawings, wherein similar numerals represent similar parts.

In the drawings:

FIG. 1 is a schematic diagram showing methods of applying the apparatus of the present invention;

FIG. 2 is an end elevational view of a preferred embodiment of the invention;

FIG. 3 is a cross-sectional view takenv along the lines 3-3 of FIG. 2;

FIG. 4 is a fragmentary cross-sectional view of the apparatus of FIG. 3, showing it in an alternative position; and

FIG. 5 is a fragmentary elevation-a1 view of a modified form of the invention.

Referring now to the drawings in detail, in FIG. 1, the preferred apparatus for carrying out the present invention, designated generally as 10, is shown in two alternative positions in duct 11. At the left, it is being towed by the hose 12 toward the opening 13 in duct 11; at the right, it is being pushed away by the hose 12 from the opening 13 in duct 11. In either case, the apparatus 10 is blasting in the general direction of the exhaust collecting duct 1%, where the removed materials and abrasive particlesare ultimately collected; this is accomplished by adjusting the blast nozzles of the apparatus in a manner described below.

A preferred embodiment of the apparatus is shown in FIGS. 2 and 3. It comprises a hollow shaft 14, rotatably supported by ball bearings 15, 16 mounted in a bearing housing 17. Said hollow shaft 14 is closed at end 18 by a hub 19 affixed thereto. A pair of tubular arms 20, 21 extend radially from said hub 19, in fluid-communicating relationship with said hollow shaft 14, as shown in FIG. 3. If desired, I may provide more than two such arms, preferably on equiangular spacing for stability reasons. Each of said arms 2h, 21 is provided with male threads 22, 23. Caps 24, 25, having mating female threads, are threaded onto the ends of arms 29, 21, forming closures for the ends thereof. Each cap 24, 25 contains at least two nozzles, a substantially tangential propulsion nozzle 26, 27 having suitably limited fluid flow capacity and being adapted to produce substantial tangential thrust for rotation of saild hollow shaft 14 at a suitable speed; and in addition a blast nozzle 28, 29 so directed as to possess both axial (i.e. aligned with the axis of hollow shaft 14) and radial components and being so oriented as to emit a blast jet against the wall of a duct 11 at a substantial angle from the normal thereto, but having substantially no tangential component. It will be noted that the propulsion nozzle 26 and blast nozzle 28yare degrees apart on the cap 24. Propulsion nozzles 26, 27 are oriented for additive thrust, as best indicated in FIG. 2. Blast nozzles 28, 29 both face forward in FIGS. 2. and 3; this direction is preferred for applications such as that shown in the right side of FIG. 1.

FIG. 4 shows the opposite case, in which caps 24, 25

have been rotated to the opposite direction. In this case, the direction of rotation of hollow shaft 14 will be reversed, and the direction of blasting will also be reversed; this direction is preferred for applications such as that shown in the left side of FIG. 1.

Referring again to F168. 2 and 3, thrust bearings 311', 31 close the ends of bearing housing 17, hollow shaft 14 extending through the annular opening of thrust bearing 3!) and terminating at its open end 32 adjacent thrust bearing 31. The annular opening 33 in thrust bearing 31 is axially aligned with hollow shaft 14. A hose fitting 34 is threaded into said annular opening 33,-the inner end 35 of said hose fitting 34 being reduced in diameter to project into the open end 32 of hollow shaft 14, as shown. Hose 12 is shown attached to hose fitting 34, the fluid being admitted through said hose 12. A nut 36, threaded onto the threaded end 37 of shaft 14, retains shaft 14 longitudinally in position in bearing housing 17, as shown in FIG. 3. A plurality of screws 38 hold thrust bearing 30 in position against bearing housing 17, and one or more set screws 39 prevent its rotation. Similarly, a plurality of screws 40 hold thrust bearing 31 in position against bearing housing 17, and set screws (not shown) may also be used to prevent rotation thereof.

Bearing housing 17 is suitably supported in a cradle designated generally as 41. Said cradle 41 preferably comprises a pair of collars 42, 43, one at each end of the bearing housing 17 extending around the thrust bearings 30 and 31, respectively. Each of said collars 42, 43 is connected by a plurality of spokes 44 to an outer rim d5, 46. Said rims 4-5, Maine in turn connected together by means of a plurality of longitudinal struts d7, each of which is fastened by screws 48 to rims 4'5 and 46, as shown in FIGS. 2 and'3. A wire cage d9, protecting the rotatable arms 20, Z1, is fastened to rim 45 by screws &3, as shown. A pair of legs Silis attached to rim di and a pair of legs 51 is attached to rim 46. Each of said legs is fitted with a caster wheel 52, as shown, to provide support for the apparatus in the manner indicated in FIG. 1.

FIG. 5 shows an alternative type of nozzle arrangement for the apparatus of the present invention. This diagram represents a front view of the arm 21, similar to the view seen at the left side of FIG. 2. The only difierence is that in FIG. 5, the propulsion nozzle or orifice 27' is not attached to adjustable cap 25, but is directly attached to arm 21. In this embodhnent, the position of blast nozzle 29, and the rotational speed, may be altered independently of the position of the propulsion nozzle 27, by rotation of cap 25. In other respects, the apparatus is the same as that described above in connection with FIGS. 2 and 3.

In order to make stable adjustments of caps 24, 25, 25', it is preferred to utilize a separate threaded cap tightener 53 which abuts said cap, as shown in FIGS. 2, 3, 4, and 5.

While the exact angle of blast against the wall of the duct is not critical, I prefer it to be about 30 degrees to the wall (or 60 degrees to the normal to the wall). This moves the air and dirt ahead of the unit in the desired direction, toward the power suction induct 1%.1

The speed of rotation of arms 20, 21 is not of critical importance. It need not be high'enough to draw excesssive power or amounts of compressed fluid. It need only be high enough to permit advancing of the apparatus at a suitable speed Without missing parts of the Wall. A preferred speed of advancing the apparatus in the duct is about feet per minute, and a preferred rotational speed is about 500 r.p.m. However, these can be very considerably altered to suit circumstances.

I claim: 7

l. A blast cleaning apparatus forcleaning the interior surface of a duct, comprising: a hollow rotatable shaft, closed at one end; means for supplying blast-cleaning fluid under suitable pressure to the other end of said hollow shaft; external bearing means rotatably supporting said. hollow shaft, and adapted substantially for axial alignment in said duct; means for advancing said bearing component, and being adapted to produce sufficient tangential thrust for rotation of said hollow shaft at a suitable speed; and a blast nozzle on each of said arms, so directed as to possess principally axial and radial components, as well as a tangentialco-mponent opposed to that of said propulsion nozzle but insuflicient to overcome the thrust of the latter nozzle, while being suitably oriented to emit a blast jet against the wall of saidduct at a substantial angle from the normal thereto.

2. A blast cleam'ng apparatus for cleaning the interior surface of a duct, comprising: a hollow rotatable shaft, closed at one end; means for supplying blast-cleaning fluid under suitable pressure at the other end of said hollow shaft; external bcaringmeans rotatably supporting said hollow shaft, and adapted substantially for axial alignment in said duct; means for advancing said bearing means and hollow shaft longitudinally within said duct; a multiplicity of closed-ended tubular arms extending radially from said hollow shaft in fluid-communicating relationship therewith; a substantially tangential propulsion nozzle on each of said arms, having suitably limited flow capacity and being adapted to produce sufiicient tangential thrust for rotation of said hollow shaft at a suitable speed; and a blast nozzle on each of said arms, so directed as to possess principally axial and radial components, as well as a tangential component opposed to that of said propulsion nozzle but insufiicient to overcome the thrust of the latter nozzle, while being suitably oriented to emit a blast jet against the wall of said duct at a substantial angle from the normal thereto.

References Cited in the file of this patent UNITED STATES PATENTS 1,717,986 Liebau June 18, 1929 1,723,014 Dahllof Aug. 6, 1929 2,358,557 Boyd et al. Sept. 19', 1944 2,418,045 Neider Mar. 25, 1947 2,557,206 Spender June 19, 1951 FOREIGN PATENTS 816,481 Great Britain July 15, 1959 

2. A BLAST CLEANING APPARATUS FOR CLEANING THE INTERIOR SURFACE OF A DUCT, COMPRISING: A HOLLOW ROTATABLE SHAFT, CLOSED AT ONE END; MEANS FOR SUPPLYING BLAST-CLEANING FLUID UNDER SUITABLE PRESSURE AT THE OTHER END OF SAID HOLLOW SHAFT; EXTERNAL BEARING MEANS ROTATABLY SUPPORTING SAID HOLLOW SHAFT, AND ADAPTED SUBSTANTIALLY FOR AXIAL ALIGNMENT IN SAID DUCT; MEANS FOR ADVANCING SAID BEARING MEANS AND HOLLOW SHAFT LONGITUDINALLY WITHIN SAID DUCT; A MULTIPLICITY OF CLOSED-ENDED TUBULAR ARMS EXTENDING RADIALLY FORM SAID HOLLOW SHAFT IN FLUID-COMMUNICATING RELATIONSHIP THEREWITH; A SUBSTANTIALLY TANGENTIAL PROPULSION NOZZLE ON EACH OF SAID ARMS, HAVING SUITABLY LIMITED FLOW CAPACITY AND BEING ADAPTED TO PRODUCE SUFFICIENT TANGENTIAL THRUST FOR ROTATION OF SAID HOLLOW SHAFT AT A SUITABLE SPEED; AND A BLAST NOZZLE ON EACH OF SAID ARMS, SO DIRECTED AS TO POSSESS PRINCIPALLY AXIAL AND RADIAL COMPONENTS, AS WELL AS A TANGENTIAL COMPONENT OPPOSED TO THAT OF SAID PROPULSION NOZZLE BUT INSUFFICIENT TO OVERCOME THE THRUST OF THE LATTER NOZZLE, WHILE BEING SUITABLY ORIENTED TO EMIT A BLAST JET AGAINST THE WALL OF SAID DUCT AT A SUBSTANTIAL ANGLE FROM THE NORMAL THERETO. 